The Stellar Gain Cell DAC (SGCD) utilises a of the shelf ESS Sabre chip. It handles both DSD and PCM for direct A/D conversion, but it requires to be set-up or reset for that, which the Stellar should handle. My Stellar Gin Cell DAC switches between PCM and DSD (USB DoP) not to bad, with the same problems you encounter. But I utilise BitPerfect not Roon.
I am not sure if the SGCD requires a control signal from the USB source or if the SGCD analyses the incoming information and detects what format it is (would be kind of difficult). But it seems to me that the SGCD does not receive a clear control signal or information allowing it to recognise the fie format. which seems to keep the SGCD in the software loo for file format recognition or something, which can only be exited by resetting the SGCD (power off and on again).
The only issues I have when switching to a different album or format is that the SGCD seems to not to empty the “digital lens” (information buffer allowing the SGCD to extract the information based on it’s own internal clock, reducing jitter) into a non signal path (trash) but into the DAC high causes short fractions of music being played. When the fractions are log enough you can recognise the music, when they are rather short it sounds like thumps, luckily in my case the fractions are long enough, not to come across as irritating thumps.
I ran firmware CPU 188.8.131.52 and currently operate CPU 184.108.40.206 (control chips) in the SGCD, perhaps you have another firmware version.